Identification of the Transient Phase of Cutting by the Specific Cutting Force and Acoustic Emission During Metal Cutting

Abstract

The stability of material processing during cutting concerns the continuity and coherence of the material processing conditions. A stable process results in predictable outputs such as cutting force and surface quality (roughness, integrity, texture). However, cutting processes encounter a transient phase before the cutting conditions reach their expected state. For example, during microcutting, material temporarily accumulates before the cutting edge is removed, resulting in outputs that differ significantly from what was anticipated. The aim of this paper is to provide a set of in-process parameters that can effectively indicate the transient phase of cutting. A statistical exploratory approach was utilized: face grooving tests were repeatedly conducted under the same nominal conditions and evaluated based on data deviation around the dataset's local mean. The specific cutting force and specific acoustic emission (AE) were chosen as indicative in-process parameters; additionally, the former is a common parameter used to describe the machinability of metal alloys, and the latter relates to the dynamic conditions (vibrations) of the material processing. The null hypothesis was that the specific cutting force and specific AE, as functions of the uncut chip thickness, have a uniform deviation from the predicted value within given ranges of the uncut chip thickness. A one-sample Student's t-statistic was performed on the datasets to assess the acceptability of the null hypothesis. Results of the t-statistic and the corresponding confidence intervals (CIs) indicate that there is a significant change in data distribution below what the literature describes as the minimum uncut chip thickness.